Cooking temperature and power control

ABSTRACT

A system and method for controlling the power delivered to cookware by a power control system that comprises a heating control user interface that is set by the user to a particular heating control user interface set point within an operating range. A controller derives from the heating control user interface set point a desired cookware temperature set point, and, over at least a first portion of the operating range that encompasses the boiling range, also derives from the heating control user interface set point a maximum limit of power that can be delivered to the cookware to maintain the cookware at the desired cookware temperature set point. The maximum power limit varies monotonically over the first portion of the operating range.

CROSS-REFERENCE TO RELATED APPLICATIONS

This application is a continuation of application Ser. No. 13/074,400,filed on Mar. 29, 2011. The disclosure of this prior patent applicationis incorporated herein in its entirety.

FIELD

This disclosure relates to controlling cooking operations.

BACKGROUND

Cooking results can be improved by knowledge of the temperature of thefood being cooked, or of the cookware itself. In electrically-operatedcooktops, such as induction and resistive cooktops, temperature can becontrolled by controlling the power delivered to the electric heatingelement. In gas cooktops, temperature can be controlled by controllingthe flow of gas to the burner. However, since temperature control is notvery effective at controlling boiling vigor, temperature-based cookingpower control systems are not able to provide the user desired controlover boiling vigor.

SUMMARY

In general, one aspect of the disclosure features a system forcontrolling the power delivered to cookware by a power control systemthat comprises a heating control user interface that is set by the userto a particular heating control user interface set point within anoperating range. The system comprises a controller that derives from theheating control user interface set point a desired cookware temperatureset point, and that, over at least a first portion of the operatingrange that encompasses the boiling range, also derives from the heatingcontrol user interface set point a maximum limit of power that can bedelivered to the cookware to maintain the cookware at the desiredcookware temperature set point, wherein the maximum power limit variesmonotonically over the first portion of the operating range.

Various implementations may include one or more of the followingfeatures. The first portion of the operating range may be from about100° C. to about 150° C. The controller, over a second portion of theoperating range, may control the power delivered to the cookware tomaintain the desired cookware temperature. The second portion of theoperating range may comprise temperatures above the first portion of theoperating range, and may further comprise temperatures below the firstportion of the operating range. The monotonic variation in the maximumpower limit may comprise a monotonic increase in the maximum powerlimit. The first portion of the operating range may be defined by alowest temperature and a highest temperature, and the maximum powerlimit over the first portion of the operating range may define amonotonically increasing curve from the lowest to the highesttemperature. The curve may define a relatively steep slope proximateboth the lowest and highest temperatures, and a less steep slope overthe rest of the first portion of the operating range. The maximum powerlimit at the lowest temperature may be about 0% of the power that can bedelivered to the cookware by the power control system, and at thehighest temperature may be about 100% of the power that can be deliveredto the cookware by the power control system. Under a predeterminedcondition the controller may cause delivery to the cookware of morepower than the maximum power limit. The predetermined condition maycomprise reaching and maintaining at least the lowest temperature of thefirst portion of the operating range.

Various additional implementations may include one or more of thefollowing features. The heating control user interface may comprise aone-dimensional control device, which may be a virtual slider. Thecontroller may define a maximum delivered power control arrangementcomprising first and second temperature servo controls and a functionthat defines a particular maximum delivered power based on the desiredtemperature set point. The system may further comprise a temperaturesensor that determines the cookware temperature, and the controller mayselect the maximum delivered power as the minimum of first and secondcontrol sub-arrangements, wherein the first control sub-arrangementcomprises the first temperature servo control inputted with the desiredtemperature set point and the cookware temperature, and the secondcontrol sub-arrangement comprises the maximum of the second temperatureservo control inputted with a fixed temperature and the cookwaretemperature, and the function that defines a particular maximumdelivered power based on the desired temperature set point. The functionthat defines a particular maximum delivered power based on thetemperature set point may comprise a lookup table.

In general, in another aspect the disclosure features a system forcontrolling the power delivered to cookware by a power control systemthat comprises a heating control user interface that is set by the userto a particular heating control user interface set point within anoperating range. The system comprises a controller that derives from theheating control user interface set point a desired cookware temperatureset point, and that, over a first portion of the operating range that isfrom about 100° C. to at least about 120° C., also derives from theheating control user interface set point a maximum limit of the powerthat can be delivered to the cookware to maintain the cookware at thedesired cookware temperature set point, wherein the maximum power limitdefines a monotonically increasing curve over the first portion of theoperating range, wherein the curve defines a relatively steep slopeproximate both the lowest and the highest temperatures of the firstportion of the operating range, and a less steep slope over the rest ofthe first portion of the operating range. The controller, over a secondportion of the operating range that comprises all temperatures below thelowest temperature of the first portion of the operating range and alltemperatures above the highest temperature of the first portion of theoperating range, controls the power delivered to the cookware tomaintain the desired cookware temperature.

In general, in another aspect the disclosure features a method ofcontrolling the power delivered to cookware by a power control systemthat comprises a heating control user interface that is set by the userto a particular heating control user interface set point within anoperating range. A desired cookware temperature set point is derivedfrom the heating control user interface set point. Over a first portionof the operating range that encompasses the boiling range, the methodfurther comprises also deriving from the heating control user interfaceset point a maximum limit of power that can be delivered to the cookwareto maintain the cookware at the desired cookware temperature set point,wherein the maximum power limit varies monotonically over the firstportion of the operating range.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a schematic, partially cross-sectional diagram of a cookingtemperature and power control system for cookware that is heated by aninduction heating system.

FIGS. 2A and 2B are functional block diagrams of a control arrangementemployed in the cooking temperature and power control system of FIG. 1.

FIG. 3 depicts a translation of the cooking system user control orheating control user interface setting into two outputs—set pointdesired cookware temperature and maximum output power limit.

FIG. 4 illustrates the output power and cookware temperature over timefor an example that illustrates the cooking temperature and powercontrol.

DETAILED DESCRIPTION

Cooking temperature and power control system 10, FIG. 1, uses a singleone-dimensional user control to automatically control both thetemperature of inductively-heated cookware 20 as well as the powerprovided to cookware 20; power control allows control of the vigor atwhich the cookware contents boil. Cookware 20 is located on cooktop 40.Induction cooking system 50 provides controlled amounts of power tocookware 20. Although the embodiment depicted in FIG. 1 uses electricalenergy to provide the power that heats the cookware, and operatesinductively, neither the source of power nor the manner in which thepower is provided to the cookware are limitations of the disclosure.System 10 is able to control the provision of power to cookwareregardless of the source of power (whether electrical or gas, forexample) or the manner in which the power is provided to the cookware(electrically via induction or resistive heating, or by burning acooking gas, for example).

Cookware 20 comprises inner wall 22 that heats food, water or othersubstances located in cookware 20 within cavity 21 formed by wall 22.Cookware 20 further comprises outer wall 26. Preferably outer wall 26 ismade fully or partially from a material that is not heated by thetime-varying electromagnetic field that emanates from induction coil 52.This aspect allows the energy to be focused on inner wall 22 and alsohelps to accomplish cookware that remains relatively cool on the outsideduring use. However, this disclosure is not limited to use with suchcool cookware and can be used with more traditional cookware in whichthe outer wall is hot. Outer wall 26 can be made from a plastic materialsuch as bulk molding compound, melamine or liquid crystal polymer, forexample. Inner wall 22 and outer wall 26 are preferably spaced from oneanother to define space 30 therebetween. Inner wall 22 and outer wall 26may be sealed to one another along circumferential contact area 38. Thisaccomplishes a sealed inner space or chamber 30 between walls 22 and 26.Chamber 30 can be used to house other aspects of cookware 20 and alsocan contribute to the desired thermal isolation of outer wall 26 frominner wall 22.

Target 25 is made from an electrically conductive material andpreferably a ferromagnetic material such as 400 series stainless steel,iron or the like. Target 25 is the sole or primary material that isinductively heated via induction coil 52. Preferably, heat spreader 24is directly coupled to both target 25 and inner wall 22. Heat spreader24 is made of a highly heat conductive substance such as aluminum; theuse of a heat spreader accomplishes more even heating of wall 22 thanwould be the case if target 25 was directly coupled to wall 22, althougheither arrangement is contemplated in this disclosure.

Thermal insulation 28 of a desired construction and configuration istypically located within chamber 30 and spaced from target 25.Insulation 28 helps to inhibit heat transfer from target 25 to outerwall 26. Insulation 28 may be located only on the bottom portion 27 ofouter wall 26 as shown in the drawing or may extend partially or fullyup along the inside of the upper portion of wall 26, and may fill someor essentially all of chamber 30. In one non-limiting embodiment,insulation 28 is a layer comprising an aerogel that is bounded on bothfaces by a reflective film such as a metalized plastic film in which themetal is etched in a manner to inhibit inductive heating of themetallization. This insulation is highly effective at inhibiting heattransfer between target 25 and the portion of outer wall 26 that iscovered by insulation 28. Heat transfer can be further inhibited byother constructional aspects such as creating a vacuum within space 30or filling space 30 with a material that is a poor heat conductor, forexample a gas such as argon gas. More generally, cool cookware includesthermal insulation and/or a vacuum between the inner cooking surface andthe external cookware wall, to inhibit heat transfer from the cookingsurface to the external wall. Aspects of the disclosure relate to anytype or design of such cool cookware.

Aspects of cookware 20 are further disclosed in commonly-assigned U.S.patent application Ser. No. 12/205,447, filed on Sep. 5, 2008, thedisclosure of which is incorporated herein by reference. However, thedisclosure herein is not limited to any particular type of cookware. Forexample the temperature and power control system can be used with moretraditional cookware in which the external wall is directly heated andthus at about the same temperature as the food being cooked.

Induction cooking system 50 comprises induction coil 52 located justunderneath or potentially embedded within cooktop 40. Cooktop 40 ispreferably made from a ceramic glass material as is well known in theart, but that is not a limitation as because the cookware is cool thecooktop may be made of other materials that are not as heat resistant,including materials that have not traditionally been used for cooktopssuch as solid surface countertop materials, wood, tile, laminatecountertop materials, vinyl, glass other than ceramic glass, plastic,etc. Coil drive system 54 provides power to coil 52 under control ofinduction cooking system control 56. Control 56 is preferably amicroprocessor that executes software that performs mathematical orlogical operations. The use of a controller to control operation of acoil drive for an induction coil in an induction cooking system is knownin the art. Aspects of system 50 are further disclosed incommonly-assigned U.S. patent application Ser. No. 12/335,787, filed onDec. 16, 2008, the disclosure of which is incorporated herein byreference.

Cookware temperature sensing is accomplished at one or more locations ofthe cookware. Temperature sensing can be accomplished with directcontact temperature sensors such as thermocouples or thermistors, forexample. Temperature sensing can also be accomplished with non-contactindirect sensors such as optically-based temperature sensors (e.g.,infrared sensors). In the non-limiting embodiment depicted in FIG. 1,direct contact temperature sensor 31 is coupled to target 25 eitherdirectly, or indirectly via a temperature conductive substance such asheat conductive epoxy. Temperature sensor 31 determines the temperatureof target 25 at the location of temperature sensor 31. Alternatively,temperature sensor 31 could be located on the side of inner wall 22facing chamber 30, or could be located elsewhere in chamber 30 at alocation where the temperature sensor was exposed to one or more heatedportions of the cookware. A non-contact sensor such as an optical sensorcould be located spaced from target 25 and/or inner wall 22, for examplein chamber 30 or in or on the inside of outer wall 26; location in or onouter wall 26 may simplify communication of the sensed temperature dataoutside of cookware 20 as explained below.

Cookware 20 further comprises wireless transmitting device 32 that isoperatively connected to the one or more temperature sensors 31 toreceive sensed temperature data therefrom. This is one means oftransferring data representative of a cookware temperature from thecookware to an external device such as induction cooking system 50, toallow the data to be further employed. In one implementation, device 32may be an RF enabled microcontroller that communicates via RF with RFtransceiver 66. Power can be provided to device 32 using coil 33 that isoperatively connected to wireless transmitter 32. Coil 33 is inductivelycoupled to and derives power from the electromagnetic field that isoutput by induction coil 52. When such an energy pick-up coil 33 isused, it may be physically located closer to induction coil 52 thanshown in the drawing, for example, embedded within or just below or ontop of the lower portion 27 of cookware outer wall 26. Physicalproximity accomplishes better coupling.

The temperature may alternatively or additionally be sensed remotelyfrom the cookware, particularly in cases in which the outer surface ofthe cookware is hot. For example, temperature may be sensed in astructure that is in thermal contact with the cookware. One example isthe cooktop. This could be accomplished with temperature sensor 60located just below or embedded within or even on the top surface ofcooktop 40 underneath the location at which cookware 20 will be locatedduring use of the induction coil. The output of temperature sensor 60 isprovided to system control 56. The disclosure is not limited to anyparticular means of sensing cookware temperature. As an additionalexample, temperature can be detected remotely from the cookware, e.g.,via an infrared sensor located in the vicinity of the cooktop such asmounted to a fume hood. Further, the system can use an absolute cookwaretemperature as described above, or could use a relative cookwaretemperature that is offset from the actual temperature as long as theoffset from actual temperature was known, at least approximately.

FIGS. 2A and 2B are functional block diagrams of one example of acontrol arrangement that can be employed in the cooking temperature andpower control system of FIG. 1. Cooktops have a cookware heating controluser interface, which is typically a one-dimensional manuallymanipulated device such as a knob that is turned, or a physical orvirtual (e.g., capacitively-operated) slider or similar manuallyoperated control. User-operated heating control user interface 58 isshown in FIG. 1. Heating control user interface 58 can have atemperature set point indicator or a power set point indicator or can bean arbitrary scale. In the non-limiting example herein heating controluser interface 58 has an arbitrary scale of 0-100. The heating controluser interface set point is interpreted (either by user control 58itself or by system control 56) to derive one or more control outputsthat are provided to coil drive system 54 so as to accomplish control ofthe amount of power delivered to cookware 20.

Heating control user interface 58 is used to control both the cookwaretemperature and the maximum limit of power that is delivered to thecookware—at least in certain circumstances and within a predetermined(first) portion of the user interface operating range. In an embodimentthis portion of the operating range is around the boiling point, wherecookware temperature is not a reliable indicator of the vigor of theboil and thus power control is needed in order to allow control ofboiling vigor. In this embodiment, at user interface set pointtemperatures that are below and above this first portion of theoperating range, the system controls the power delivered to the cookwareso as to hold the cookware temperature constant at the desired cookwaretemperature set point.

The embodiment of the control arrangement shown in FIGS. 2A and 2B worksas follows. The inputs are the heating control user interface settingand the measured cookware temperature. The heating control userinterface setting is preferably interpreted (e.g., using a lookup table,not shown) as a desired cookware temperature set point; this temperatureset point is then provided as one of the two variable inputs to thecontrol arrangement. For heating control user interface temperaturesettings that are below or above a predefined (first) temperature range(e.g., above or below the range around boiling described above, which inone non-limiting example is from about 100° C. to about 150° C.),temperature servo control 80 is used by system control 56 to control thepower delivered by coil drive system 54 to coil 52, and thus to controlthe power delivered to the cookware. The inputs to servo control 80 arethe heating control user interface setting (specifically, the desiredcookware temperature set point that is derived from the setting ofheating control user interface 58), and the measured cookwaretemperature. The output of servo control 80 is a control signal that isused to control the power delivered to the cookware. Temperature servocontrol 80 thus governs the power setting so as to quickly bring thetemperature up to the desired set point, and then hold the sensedcookware temperature constant at the desired set point.

There are many possible control laws that could be used to accomplishthe temperature servo controls in the control arrangements shown inFIGS. 2A and 2B, as is known in the field. In an embodiment, servocontrol 80 is accomplished with a PID controller. A PI controller orother controllers known in the field that could accomplish the statedresults could be used instead. Typically, the control law results infull power being provided to the cookware until the temperature is closeto the desired set point, so that the food is quickly heated to thetemperature set point. Temperature-based PID controllers for cookwareare known in the art and so will not be further described herein. Thegains used in the PID controllers depend on the particular hardware usedin the cooktop and the cookware. For servo control 80 and the other twotemperature-based control loops in the control arrangement shown inFIGS. 2A and 2B (servo controls 92 and 98), other types of controllersthat are able to maintain a measured cookware temperature based on atemperature set point can be used. As one non-limiting example, PIcontrollers with zeros at 0.01 Hz can be used for the three temperatureservo controls.

For heating control user interface settings that are within thepredefined temperature range around boiling, control arrangement 90,FIG. 2B, is employed by system control 56. Arrangement 90 includes twotemperature servo controls 92 and 98, both of which may be PI or PIDtemperature controllers, each of which is similar to servo control 80.The inputs to servo control 92 are the boiling temperature (nominally100° C.) and the measured cookware temperature. Servo control 92 thus isable to keep the cookware temperature at 100° C. The inputs to servocontrol 98 arc the heating control user interface setting (specifically,the desired cookware temperature set point that is derived from thesetting of the heating control user interface) and the measured cookwaretemperature. Servo control 98 thus is able to keep the cookwaretemperature at the desired user set point. The third control aspect ofarrangement 90 is power lookup table 94. The heating control userinterface setting (specifically, the desired cookware temperature setpoint that is derived from the setting of the heating control userinterface) is used to select the value for maximum available outputpower limit from LUT 94. Typically the output of LUT 94 is a powersetting that monotonically rises with the user interface setting. Analternative to a LUT could be a function enabled by system control 56that calculated a power based on the setting of heating control userinterface 58. Also, the functions of both LUT 94 and the LUT (not shown)that is used to derive a desired temperature set point from the settingof the heating control user interface could be accomplished with asingle lookup table, or in other manners that would be apparent to thoseskilled in the field such as via calculations based on the user setting.

The power that is actually provided to the cookware is then determinedby selection of the minimum (block 100) of two values: the first valueis the maximum (block 96) of the outputs of servo control 92 and LUT 94,and the second value is the output of servo control 98.

In an ideal sense the control scheme accomplished with servo control 80could be accomplished by control arrangement 90, which would make servocontrol 80 superfluous. In this case, a beginning integral value for thePID controllers may need to be calculated when control passes from LUT94 to a PID controller (or to any other PID-style controller that islike a PID controller in that it needs an input integral value), asthere would be no previous integral value for use as an input to the PIDloop. This calculation would be apparent to those skilled in the field.Once the initial condition of a PID-style controller (the last integralvalue) is provided, it creates its own input integral value from itsoutput, so this calculation would only need to be done when control wasfirst passed to the PID-style controller.

An example of the heating control user interface settings, thecorresponding output power provided to the cookware, and the desiredcookware temperature set point that is derived from the heating controluser interface setting, is shown in FIG. 3. For heating control userinterface settings between the lowest value (0) and the value labeled“A”, and from the value labeled “B” up to the maximum value of 100, theoutput power limit (shown as graph line 110) is 100%. For settingsbetween A and B the maximum output power limit increases monotonicallyover the A-B range from about 0% to 100% of the power that can bedelivered to the cookware by the power control system. In one example,value A corresponds to the boiling point (nominally 100° C.) and value Bcorresponds to about 150° C. Graph line 112 shows the set point desiredcookware temperatures (i.e., the “user setting” input to the controlarrangement shown in FIGS. 2A and 2B) that correspond to the heatingcontrol user interface settings for the example illustrated in FIG. 3.

In the A to B temperature range the control law enabled by systemcontrol 56 controls the power provided to the cookware within a cookwaretemperature range bounded on the low end by point A and on the upper endby the temperature that corresponds to the heating control userinterface setting (which is greater than A and less than B, labeled “S”in FIG. 3). The variable power level in the A-B range accomplishesbetter control over the vigor of boiling than does control based on atemperature-based control law as is used from 0 to A and from B to 100.The A to B temperature range includes the measured temperature at whichboil begins and occurs, and extends for a desired temperature rangeabove the boiling point to point B. The range selected would be specificto the hardware. For example, in cases in which the cookware temperatureis measured (as opposed to, say, cases in which the food temperature ismeasured), the measured temperature may not correspond to the foodtemperature. In the example illustrated in FIG. 1, the measuredtemperature is the temperature of the target, which is typically hotterthan the food. A target temperature of 110° C. may correspond to a foodtemperature of around boiling, which can be used as point A. Boilingpoint variations dependent on elevation should also be taken intoaccount. Typically, point A will be selected to be just below boiling(e.g., potentially in the range of from about 90° C. to about 110° C.);a higher value will cause sudden boiling and a lower value will causeslower heating times, especially for low power settings. Typically,point B is selected to achieve a cookware content temperature of around150° C.; a higher value limits the cooking capabilities of the systembecause it slows heat-up time for any temperatures between A and B,while a lower value reduces the power resolution in the A-B range andthus results in poorer control of boil vigor. Point B is the maximumtarget temperature at which power is directly controlled by the user,and thus is the end point for direct control over boiling vigor.Depending on the construction of the cookware and where on the cookwarethe measured temperature value is taken, point B could potentially rangedown to closer to boiling (e.g., around 100° C. to around 120° C.) up toaround 150° C. or perhaps higher. In a case in which the targettemperature of induction cookware is the measured temperature value,point B will likely fall in the range of from about 120° C. to about170° C.

The power control arrangement employed in this A to B range providesresolution which allows control over the vigor of boiling; this controlcan be accomplished over a desired range of boiling characteristics. Forexample, the range can be enabled from simmer (which actually begins afew degrees below the boiling point) through a vigorous rolling boil.The width or scale of the A to B temperature range should be largeenough to allow for a desired power control granularity; a wider rangeis thus at least theoretically better. However, a functional tradeoffassociated with the dual set point control arrangement over the selectedA to B temperature range is the time period over which the food comes upto temperature when the desired temperature is in the A to B range andthe food does not go through a phase change. As the control schemeprovides less than full power over the A to B temperature range, heatingof the food is slowed as compared to a standard temperature servo. Thistradeoff thus suggests a relatively narrow A to B range. In practice theupper end of the range can be about 150° C. because not many foods arecooked in the range from above boiling up to about 150° C., so thepractical risk associated with the longer heat-up time is minimal.

The slope of the power curve in the A-B range is selected to achieve adesired result. The slope can be greater around the end points becauselower powers typically are not sufficient to maintain boil so finecontrol is not useful close to A, and small changes in high power closeto B have little effect on the apparent vigor of the rolling boil aroundpoint B. Increasing slope around A and B allows a flatter curve acrossmost of the midrange, providing the user with finer control over thepower provided to the cookware and thus better control over the vigor ofthe boil. Other mappings of heating control user interface settings topower in the A-B range are contemplated herein. Typically, though, thefunction monotonically increases over the range so that the powerincreases as the control is turned up, as would be expected in cooktopoperation.

The disclosure contemplates mapping the position of the heating controluser interface to both a temperature set point and a provided outputpower value, over at least a portion of the system operating range. Thismapping could be accomplished in other manners that would be apparent tothose skilled in the field. For example, the values could be calculatedby controller 56 using predetermined algorithms that were appropriatefor the selected hardware.

The disclosure herein contemplates the use of one, or perhaps more thanone, cookware temperature range over which power delivered to thecookware is controlled per se, rather than control to a temperature setpoint. Most commonly, but not necessarily, the boiling range will beincluded, as it is here where fine control over the energy is useful toprovide better control over boiling vigor. The available output powerfunction over relevant temperature range(s) need not be as depicted inFIG. 3. Rather, any function that achieves a desired power control overthe selected temperature range(s) can be used, and enabled by systemcontrol 56.

FIG. 4 shows the provided output power (graph line 120) and cookwaretemperature (graph line 122) over time t0 (when the heating control userinterface is set by the user) to t5 (when long term steady statetemperature has been reached) for an example that illustrates anembodiment of the cooking temperature control. In the example, theheating control user interface is set to a value (“S”, FIG. 3) whichcorresponds to 140° C. and a limit of 80% of maximum available outputpower. This setting (above 100° C. and below 150° C.) puts the controlin the realm of arrangement 90, FIG. 2B. Boiling is indicated as 100°C., but could actually be higher than that: since the target is hotterthan the food being cooked, when the target temperature is measured asopposed to the temperature of the contents of the cookware, the measuredtemperature at boiling will actually be above 100° C.

From time t0 to t1 (when the measured temperature reaches thetemperature of boiling), the output (coil 52) power remains at 100%while the cookware temperature increases to boiling (nominally 100°C.)—this 100% output power is the servo control 92 output. During thistime period the output of servo control 98 is also at 100%, so that as apractical matter either servo control 92 or servo control 98 could be incontrol. In a non-ideal sense as the cookware temperature approaches100° C. servo control 92 will request less than 100% power while servocontrol 98 requests 100% power, giving control (because of minimumselection function 100) to servo control 92.

From t1 to t2 the power falls off to 80% while the cookware remains atboiling temperature. In this time period servo control 92 remains incontrol, as its output is greater than the 80% output of lookup table 94(and thus is selected by maximum selection function 96), while theoutput of servo control 98 remains at 100% (and thus is deselected byminimum selection function 100). Power decays gradually because thetemperature of the contents of the cookware lags that of the target, andas that temperature difference decreases the power required to maintainthe target temperature at boiling (nominally 100° C.) decreases.

From t2 to t3 lookup table 94 is in control since its output (80%) isgreater than the output of servo control 92 and less than the output ofservo control 98. The output power thus remains at 80%, which causes thecookware to heat up until it reaches a new intermediate steady statevalue. One reason for the increase in temperature is that in the examplefor the cookware to remain at 100° C. requires less than 80% power. At80% power, the target temperature will increase above 100° C., the boilvigor will increase and more steam will be created (the energy that doesnot maintain the boil goes into the creation of steam), and the targetwill eventually settle at a higher temperature. The rise in measuredcookware temperature is similar to the reason the power dropped offbetween t1 and t2, except this time power is kept the same (at 80%), andtemperature is allowed to rise.

From t3 to t4, because the temperature is less than the set point, servocontrol 98 remains at 100%. Thus, lookup table 94 is in control and thepower remains at 80%. The cookware contents are dry enough that thetemperature begins to increase above where it was during boiling, to the140° C. user interface desired cookware temperature set point.

From t4 to t5 the temperature is at the desired cookware temperature setpoint, so servo control 98 causes the power to drop off to some levelbelow 80% at which the cookware temperature is maintained at the 140° C.set point. The steady state output power value (“X”) is indeterminate asit depends on the hardware construction, and the cookware contents. Thegradual power decay from t4 to t5 is the effect of two aspects. One isthat servo control 98 has taken over. The other is that, like when thesystem approached 100° C. and servo control 92 slowly reduced powerbecause of the objects around the cookware, now servo control 98 isdoing the same thing. The difference this time is that lookup table 94is not in control because its 80% output power is greater than X, and solookup table 94 does not stop the drop in power.

The disclosure herein relates to methods of cooking other than inductioncooking. The disclosure involves control of the power provided to thecookware, regardless of the particular energy source or the manner inwhich the energy is delivered to the cookware. For example, electricalenergy is used to heat cookware in both induction and resistance-basedcooktops; the control scheme herein can be used with either type ofelectric cooktop. Also, gas is used to deliver the cooking energy in gascooktops, and the gas flow rather than output power can be thecontrolled variable in the control scheme herein as a means to controlthe power delivered to the cookware. The disclosure herein controls theprovision of power to the cookware so as to allow control of thecookware temperature and the vigor at which the contents boil.

A number of embodiments and options have been described herein.Modifications may be made without departing from the spirit and scope ofthe invention. Accordingly, other embodiments are within the claims.

What is claimed is:
 1. A device configured to operate a cooking system used for heating a cooking utensil, where the cooking system comprises a temperature sensor that senses a temperature of the cooking utensil, and a user-manipulated heating control user interface that is used to establish a user control setting, the device comprising: a controller that is input with: (i) the sensed temperature of the cooking utensil, (ii) the user control setting, and (iii) a particular temperature representing the boiling point, where the controller is configured to: determine, based on all three of the inputs to the controller, a command to control the heating of the cooking utensil; and output the command to the cooking system.
 2. The device of claim 1 wherein the controller comprises: a first temperature servo having as inputs: (i) the sensed temperature of the cooking utensil, and (ii) the user control setting, the first temperature servo providing an output power command that if applied to a heating element of the cooking system would cause the cooking utensil temperature to follow the user control setting; a first processing block having the user control setting as an input, the processing block setting a maximum power output that can be applied to the cooking utensil associated with the user control setting; and a second temperature servo having as inputs: (i) the sensed temperature of the cooking utensil and (ii) the particular temperature representing the boiling point; wherein the second temperature servo provides an output power command that if applied to a heating element of the cooking system would cause the temperature of the cooking utensil to follow the particular temperature representing the boiling point.
 3. The device of claim 2 wherein the controller is further configured to: determine a first maximum, the first maximum being determined as the maximum of (i) the output power command of the second temperature servo and (ii) the maximum power output of the first processing block; and determine a first minimum, the first minimum being determined as the minimum of the (i) the first maximum, and (ii) the output of the first temperature servo; wherein the output of the first minimum is provided as a command to control the heating of the cooking utensil.
 4. The device of claim 1 where the controller is configured to determine, based on all three of the inputs to the controller, a command to control the heating of the cooking utensil and output the command to the cooking system, but only over a first portion of a temperature operating range that is defined by a lowest temperature and a highest temperature, and encompasses 100° C.
 5. The device of claim 4 where there is a second portion of the temperature operating range that encompasses temperatures both above the highest temperature and below the lowest temperature of the first portion of the temperature operating range, and where in this second portion of the temperature operating range the controller is configured to determine, based on the sensed temperature of the cooking utensil and the user control setting, a command to control the heating of the cooking utensil and output the command to the cooking system.
 6. The device of claim 4 wherein the command to control the heating of the cooking utensil establishes a maximum limit of power that can be delivered to the cookware, and over the first portion of the temperature operating range the maximum power limit is entirely non-decreasing as the temperature increases.
 7. The device of claim 6 wherein over the second portion of the temperature operating range the maximum power limit is full power.
 8. The device of claim 7 wherein over at least the second portion of the temperature operating range the controller uses a control law that results in full power being provided to the cookware until the temperature is close to a desired temperature set point that is established based on the user control setting.
 9. The device of claim 1 wherein the cooking utensil comprises an inner wall that heats contents, a target that comprises an electrically conductive material and that is thermally coupled to the inner wall, and wherein the temperature sensor senses the temperature of one or both of the inner wall and the target.
 10. The device of claim 1 wherein the heating control user interface is adapted to be turned up and turned down by the user to a particular heating control user interface set point, and wherein the user control setting comprises a desired cookware temperature set point that is derived from the setting of the heating control user interface.
 11. The device of claim 1 wherein the particular temperature representing the boiling point is nominally 100° C.
 12. The device of claim 1 wherein the cooking system comprises an induction heating system and the command to control the heating of the cooking utensil comprises a command to control the power delivered to the induction heating system.
 13. The device of claim 1 wherein the cooking system comprises a resistive heating system and the command to control the heating of the cooking utensil comprises a command to control the power delivered to the resistive heating system.
 14. The device of claim 1 wherein the cooking system comprises a gas heating system and the command to control the heating of the cooking utensil comprises a command to control the flow of gas in the gas heating system.
 15. A device configured to operate a cooking system used for heating a cooking utensil, where the cooking system comprises a temperature sensor that senses a temperature of the cooking utensil, and a user-manipulated heating control user interface that is used to establish a user control setting, the device comprising: a controller that is input with: (i) the sensed temperature of the cooking utensil, (ii) the user control setting, and (iii) a particular temperature representing the boiling point, where the controller is configured to: determine, based on all three of the inputs to the controller and only over a first portion of the temperature operating range that is defined by a lowest temperature and a highest temperature, and encompasses 100° C., a command to control the heating of the cooking utensil, and output the command to the cooking system; where there is a second portion of the temperature operating range that encompasses temperatures both above the highest temperature and below the lowest temperature of the first portion of the temperature operating range, and where in this second portion of the temperature operating range the controller is configured to determine, based on the sensed temperature of the cooking utensil and the user control setting, a command to control the heating of the cooking utensil and output the command to the cooking system; and wherein the command to control the heating of the cooking utensil establishes a maximum limit of power that can be delivered to the cookware, and over the first portion of the temperature operating range the maximum power limit is entirely non-decreasing as the temperature increases.
 16. A device configured to operate a cooking system used for heating a cooking utensil, where the cooking system comprises a temperature sensor that senses a temperature of the cooking utensil, and a user-manipulated heating control user interface that is used to establish a user control setting, the device comprising: a user-manipulated user interface for interacting with the cooking system, the user interface adapted to be set by a user to settings over a user interface operating range; a controller for controlling the power applied to the cooking utensil, where the controller is input with: (i) the sensed temperature of the cooking utensil, (ii) the setting of the user interface, and (iii) a particular temperature representing the boiling point; wherein over a first portion of the operating range of settings of the user interface the controller applies power to the cooking utensil based on a difference between the sensed temperature of the cooking utensil and a temperature set point associated with the setting of the user interface, and; wherein over a second portion of the operating range of settings of the user interface, the controller applies power to the cooking utensil up to a predetermined maximum power level, where the predetermined maximum power level is associated with the setting of the user interface.
 17. The device of claim 16 wherein the cooking system comprises an induction heating system and the controller controls the heating of the cooking utensil by controlling the power delivered to the induction heating system.
 18. The device of claim 16 wherein the cooking system comprises a resistive heating system and the controller controls the heating of the cooking utensil by controlling the power delivered to the resistive heating system.
 19. The device of claim 16 wherein the cooking system comprises a gas heating system and the controller controls the heating of the cooking utensil by controlling the flow of gas in the gas heating system. 